The present invention relates to presses used to flatten dough-like material, for example edible dough materials used in tortillas, pizzas and similar food items.
Presses for dough material are well known and one type comprises a stationary press, such as disclosed in U.S. Pat. No. 4,559,002, in which individual dough pieces are placed under a vertically movable platen, the platen compresses and spreads out the dough and then the platen is moved away revealing a flattened dough piece which must be manually removed. Typically such stationary presses utilize a relatively small platen since only one, or a small number of dough pieces are being pressed at a single time.
Another type is an automated dough press which typically comprises an intermittently moving belt and a vertically reciprocating platen, such as disclosed in U.S. Pat. Nos. 5,231,919 and 5,396,833. In an indexing belt press, the belt is stopped, and while stopped the platen moves downwardly to engage and flatten a dough piece against the belt and then the platen moves upwardly. Subsequently the belt indexes to the next position to present a new series of dough pieces to the platen. Generally a large number of dough pieces, such as 12 to 20 individual dough pieces are pressed simultaneously by the platens, which are relatively large in comparison to the size used in stationary presses. Another type of automated dough press utilizes a continuously moving belt for receiving and carrying the large number of dough pieces into the press area for simultaneous flattening, and from the press area to a point of further utilization, such as disclosed in U.S. Pat. No. 6,951,451. Vertically reciprocating platens are used to press the dough pieces into flattened shapes and one or both of the platens can be heated so as to provide heat into the dough product.
The heating of the platens has been provided by electrical resistance heating elements. In stationary presses, utilizing a relatively small platen, the heating elements have been cast in place in the platen as it is formed. However, in moving belt presses, either indexing or continuously moving belt presses, the platens are substantially larger and the heating elements are provided separately, in rod shapes, and are inserted into bore holes formed in the platens after they are formed. The bore holes must be drilled with precision. That is, the bore holes must be very straight and have very tight tolerances, in order to allow the rod shaped heating elements to be inserted and later removed, as well as to be positioned very close to the wall of the bore holes. If there is too much clearance between the heating element and the wall of the bore hole, conduction of the heat from the heating element is reduced causing the heating element to overheat and prematurely fail. When a heating element fails, it must be removed, which, due to the very close tolerances, sometimes is very difficult or impossible to do, thereby requiring a new bore hole to be drilled into the platen, at a now less than optimal location for a new heating element. In the past, the concept of using cast in place heating elements in a moving belt press has not been considered at least for the reason that due to the relatively large size of the platens used in the moving belt presses, and thus the very high cost of replacing a platen should a heating element fail.